The present disclosure generally relates to gas purification systems and processes of use. More particularly, the present disclosure relates to the low pressure ammonia recovery in the gas purification systems.
In conventional industrial technologies for gas purification, impurities, such as H2S, CO2 and/or COS are removed from a gas stream such as flue gas, natural gas, syngas or other gas streams by absorption in a liquid solution, e.g., in a liquid solution comprising ammonia and/or one or more amine compounds.
Used liquid solution is subsequently regenerated in a regenerator column to release the impurities comprised in the solution, typically by countercurrent contacting with steam. The steam needed for regeneration is typically produced in the power plant turbine system. In addition, reboiling may provide further release of impurities comprised in the liquid solution.
In conventional absorption-regeneration processes as described above, regenerated and reboiled liquid solution are typically re-used in another absorption cycle. The reboiled solution may, however, have a temperature as high as 100-200 degrees Celsius (° C.). To enable efficient absorption, the liquid absorbent solutions typically requires cooling before being passed to another round of absorption. Cooling has conventionally been accomplished by heat-exchange with the used liquid solution from absorption.
In general, the energy requirements of a conventional gas purification process are of three types: binding energy, stripping energy and sensible heat. Binding energy is required for breaking the chemical bond formed between the impurities and the liquid solution, whereas stripping energy is required for production of the steam needed for releasing the impurities from the liquid solution. Sensible heat is in turn needed for heating of the liquid solution prior to regeneration. In conventional systems and processes, part of the produced energy may be lost, for example, in the system coolers, which reduce the temperature at specified locations in the system. Moreover, energy may be lost in condensers located at the top of the absorber, regenerator, and the like, and in the form of water vapor exiting the process, mostly at the top of the regenerator where water vapor is present in the purified carbon dioxide gas.
Thus, gas removal, and in particular regeneration, is an energy intensive process. As such, reduction of energy requirements at different parts of the gas purification process could potentially reduce the total energy required by the process. While various improvements of conventional gas purification technologies are known, there remains a need to further improve gas purification systems and processes, particularly with respect to reducing the energy consumption therein.